The techniques of mathematical modeling computer simulation and mathematical analysis are used to identify and study cell kinetic and pharmacokinetic issues related to leukemia, hematopoiesis and cancer chemotherapy. A new model structure has been developed for the description of simultaneous cellular differentiation, proliferation and regulatory control. Cell kinetic models have been applied to the Lukes-Collins classification of the non-Hodgkin's lymphomas. Clinical and kinetic data for immunoblastic sarcoma has been used to develop interrelationships among cell kinetics, cycle sensitivity, cell loss, immunocompetence and treatment response. Pharmacokinetic modeling and the CLINFO system have been used to classify high risk patients undergoing high dose Methotrexate and rescue protocol. A preliminary analysis of risk factors for recurrence in breast cancer has been performed, based on a comprehensive clinical data base of 103 intermediate risk patients. A maximum likelihood approach has been used to supplement our fundamental methods where data will support a biologically inspired statistical methodology rather than a detailed mathematical model structure.